Corrections & Clarifications: An earlier version of this story incorrectly spelled the name of Groupon CFO Jason Child. An update has also clarified Groupon's operating cash flow and second-quarter sales forecasts.

SAN FRANCISCO — It's hard to find a worse technology investment over the last three-and-a-half years than the Groupon IPO.

And last week the pain kept coming for retail investors who bought into the hype surrounding the online coupon pioneer in late 2011.

On May 5, Groupon GRPN reported first-quarter revenue growth of just 3% and issued a second-quarter sales forecast that was well below Wall Street estimates.

Zynga went public the month after Groupon, and by now it should be clear that neither company had a market that was as big or a business model as profitable as their investment bankers once predicted.

As Groupon CEO Eric Lefkofsky said on a conference call , in explaining why -- after six years of doing business – the company's marketplace has penetrated less than 5% of merchants: "It's hard."

While Groupon will never be what its IPO investors once expected, for those still holding its shares there are at least glimmers of hope.

The company swung to an operating profit in the first quarter and narrowed its net loss from a year earlier.

Globally, its number of customers rose 7% year-over-year, Groupon CFO Jason Child said in a phone interview.

During the 12 months ended in March, the company's operations generated cash flow of $307.8 million. That cash flow has been adjusted to exclude results of the company's South Korean unit, called Ticket Monster.

A year ago, the company was touting Ticket Monster as a growth engine. Now that the company has sold Ticket Monster, Groupon's revenue growth has evaporated, as explained in this column last month.

Groupon gave a revenue forecast for the second quarter of between $700 million to $750 million, well below the average analyst estimate of $827 million and slightly less than the $751 million it had a year earlier.

This has been the puzzle that Groupon executives have been unable to solve: Whenever the company's bottom line improves, it comes at the expense of growth.

Even so, Child, who's been with the company since 2010, still believes in the Groupon story.

"It's a multi-year effort," he told me. "We feel good about the long term."

While the company's long-suffering investors would have a hard time agreeing with that assessment, what he said next is indisputable:

"Expectations were super-high at the IPO."

John Shinal has covered tech and financial markets for more than 15 years at Bloomberg, BusinessWeek,The San Francisco Chronicle, Dow Jones MarketWatch, Wall Street Journal Digital Network and others. Follow him on Twitter: @johnshinal.